The invention is in the field of semiconductor devices, and relates more specifically to multiple semiconductor chip (hereinafter multi-chip) modules for use over a wide range of voltage and power levels.
Multi-chip module technology has recently been applied to integrated circuits used in both power and control applications, such as power supplies, power converters and electronic ballast circuits. Such multi-chip modules typically include at least an output semiconductor chip and a control semiconductor chip, mounted on an electrically conductive (typically metal) heat sink. In the prior art, one or more of the chips employed in the module must be electrically insulated from the metal heat sink in order to maintain electrical isolation, thus requiring a relatively complicated structure which is costly to manufacture.
A typical prior-art device configuration of this type is shown in Japanese patent abstract JP 6-169057A. In the elementary multi-chip module shown in this reference, one chip is shown as soldered directly to a heat sink, while a second chip is provided on an electrode plate, which is in turn provided on an insulating ceramic plate provided on the heat sink.
While the foregoing structure permits the fabrication of a multi-chip module incorporating different chip types and functions, it is relatively complicated and therefore uneconomical to manufacture, and in certain applications structures of this type will generate electromagnetic (EMI) radiation.
Another prior-art multi-chip configuration is shown in U.S. Pat. No. 6,130,458, which in FIG. 12B shows a multi-chip structure in which both the control chips and the power chip are fabricated in the same SOI (Silicon-On-Insulator) technology. In U.S. patent application No. 09/440,595, commonly-assigned with the instant application and having the present inventors in common, a multi-chip module is provided with an SOI high power chip and a bulk-substrate control chip. However, a drawback of these configurations is that heat-sink efficiency for the power chip is reduced due to the presence of an insulating layer between the active device and the conductive mounting plate.
Accordingly, it would be desirable to have a multi-chip module which is simple in construction and therefore economical to fabricate, and in which performance parameters such as heat sink efficiency and reduced EMI are enhanced.
It is therefore an object of the present invention to provide a multi-chip module for use over a wide range of applications which is simple in construction, economical to fabricate, and capable of offering enhanced performance, and in particular improved heat sink efficiency and reduced EMI.
In accordance with the invention, these objects are achieved in a multi-chip module of the type described above in which a plurality of semiconductor chips of different types are all directly mounted on an electrically conductive heat sink without the use of a separate electrical insulation layer.
In a preferred embodiment of the invention, the multi-chip module includes at least an output semiconductor chip having a bulk substrate configuration and an SOI control semiconductor chip, with both the output semiconductor chip and the control semiconductor chip being directly mounted on the electrically conductive heat sink without the use of a separate electrical insulation layer.
In further preferred embodiments of the invention, the control semiconductor chip may include BIMOS, bipolar, or CMOS devices, and the output chip may include MOS, bipolar or IGBT devices.
Multi-chip modules in accordance with the present invention offer a significant improvement in that a simple, economical configuration having improved performance characteristics such as enhanced heat sink efficiency and reduced EMI (Electro-Magnetic Interference) is achieved.
These and other aspects of the invention will he apparent from and elucidated with reference to the embodiments described hereinafter.